I think the presence of black swans in Australia also was taken as further evidence of Australia being literally the antipodes--in the sense of being completely backward/opposite from everything Europeans had "known." At least, they were still talking about that 20 years ago in Australia (maybe they're over it by now?)....

In Nassim Nicholas Taleb's definition, a black swan is a large-impact, hard-to-predict, and rare event beyond the realm of normal expectations.

The term black swan comes from the ancient Western conception that all swans were white in color. In that context, a black swan was a metaphor for something that could not exist. The 17th Century discovery of black swans in Australia metamorphosed the term to connote that the perceived impossibility actually came to pass.

The term was introduced by Karl Popper in the context of the falsifiability of the statement "All swans are white".